The present invention is adaptable for use on nearly any medical infusion device wherein medical fluids are delivered to the patient through a flexible tubing such that none of the medical fluid comes into direct physical contact with the components of the infusion device. One well known group of infusion devices used in the medical industry are peristaltic pumps. Peristaltic pumps are used in combination with disposable fluid delivery sets or cassettes. Fluid delivery sets generally consist of a cylindrical drip chamber assembly, which is connected to an inlet tube at one end and a resilient and stretchable silicone tube on the other end; a mounting member connected to the second end of the silicone tube and an outlet tube connected between the mounting member and the patient.
Peristaltic pumps are generally classified as being either a rotary peristaltic pump or a linear peristaltic pump. U.S. Pat. No. 4,913,703 granted to Pasqualucci et al discloses a rotary type of peristaltic pump and U.S. Pat. No. 4,493,706 granted to Borsanyi et al discloses a linear type of peristaltic pump, both of which are incorporated herein by reference. Rotary peristaltic pumps commonly include a motor driven rotor mounted on the front surface of the pump. The rotor carries two or more circumferentially spaced apart rollers which are designed to receive the silicone tube of the fluid delivery set mounted thereon. As the motor rotates the rotor, the spaced apart rollers are sequentially brought into contact with the silicone tube to compress portions of the silicone tube. A predetermined volume of medical fluid is contained between the compressed portions of the silicone tube so that a predetermined volume of medical fluid is advanced through the silicone tube as the rotor is rotated by the motor. Because the volume of medical fluid contained between the compressed portions of the silicone tube is a known quantity, the amount of fluid to be delivered to the patient may be regulated by controlling the rate of rotation of the rotor by the motor.
In many of the commonly available rotary peristaltic pumps, the fluid delivery set is mounted in a pair of recesses located on the front surface of the pump such that the drip chamber assembly is received in the first recess and the mounting member is received in the second recess. Once the drip chamber assembly and mounting member have been placed in the respective recesses, the silicone tube must then be stretched to position the silicone tube around the rotor of the peristaltic pump so that portions of the silicone tube are compressed by the rollers on the rotor. When the silicone tube is stretched around the rotor of the peristaltic pump, the silicone tube has a predetermined length and internal diameter.
In an effort to facilitate the mounting of the fluid delivery set on the typical peristaltic pump, the rotor is typically positioned on the front surface of the peristaltic pump so that the entire rotor is exposed. During normal movement of the peristaltic pump from a storage area to a patient's room or during ambulatory use, the peristaltic pump may be accidentally dropped or the rotor of the peristaltic pump may accidentally contact the hospital bed or another object. Although the rotor on the typical peristaltic pump is designed to withstand much of the usual contact which occurs in a hospital, the shaft which connects the rotor to the motor may be damaged. Even though the peristltic pump may continue to operate, the increased resistance caused by the damaged shaft may dramatically decrease the operating life of the motor or create an inaccurate delivery rate.
Because the fluid delivery set is typically changed every day, it is important that the fluid delivery set is manufactured according to fairly rigid manufacturing specifications. The silicone tube of the fluid delivery set is selected so that the internal diameter of the silicone tube will be consistent for each fluid delivery set when the silicone tube is stretched and positioned around the rotor. Oftentimes, the length and diameter of the drip chamber assembly will vary between different manufacturing lots. Because the drip chamber assembly is typically mounted on the peristaltic pump by inserting the bottom end of the drip chamber assembly into a first recess, the top end of the drip chamber assembly may not be properly aligned with the drop sensors on the peristaltic pump. This may result in an incorrect reading of the fluid drops by the drop sensors so that the drop sensors on the peristaltic pump may indicate that there is a flow error and automatically disconnect the motor on the peristaltic pump.
With many of the commerically available peristaltic pumps, the fluid delivery set may be improperly mounted around the rotor if the drip chamber assembly and/or the mounting members are improperly positioned in the respective recesses. With certain peristaltic pump designs, it is also possible for the silicone tube to fall off the rollers of the rotor if the patient accidentally displaces the mounting member or drip chamber assembly from the respective recess during operation of the peristaltic pump. In these situations, it is possible to have an uncontrolled flow of medical fluid to the patient because the rollers of the rotor are not properly compressing the silicone tube to restrict the flow of fluid through the fluid delivery set. If the peristaltic pump is being used to deliver enteral fluid to a patient, the uncontrolled infusion of enteral fluid to the patient may result in aspiration of the fluid into the patient's lungs or over infusion of the enteral fluid.
At present, only one commerically available peristaltic pump includes a safety mechanism to detect the improper mounting of the fluid delivery set on the peristaltic pump. This safety mechanism is disclosed in U.S. Pat. No. 4,913,703 which is assigned to the assignee of the present invention, Sherwood Medical Company. As disclosed in U.S. Pat. No. 4,913,703, the operation of the pump motor is prevented when the fluid delivery set is not detected by the peristaltic pump. Additionally, an alarm will sound if the user attempts to operate the peristaltic pump if the fluid delivery set is not properly mounted on the peristaltic pump.